Tree-ring-based reconstruction of larch budmoth outbreaks in the Central Italian Alps since 1774 CE (original) (raw)
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Spatiotemporal heterogeneity of larch budmoth outbreaks in the French Alps over the last 500 years
Canadian Journal of Forest Research, 2017
In the subalpine forest ecosystems of the French Alps, European larch trees (Larix decidua Mill.) are periodically affected by outbreaks of a defoliating insect, the larch budmoth (Zeiraphera griseana (Hübner, 1799); LBM). To assess the long-term dynamics of LBM populations, we propose a spatiotemporal analysis of a long outbreak chronology reconstruction for the entire French Alps covering the period 1414-2009. This chronology was obtained by analyzing tree ring width (TRW) chronologies collected from 44 larch populations. The evidence of a latitudinal gradient in LBM is an original result that we have related to the "travelling waves" and "epicenter" theory. Wavelet analyses revealed a strong explicit continuous signal for periodicities of 4, 8, and 16 years throughout the entire 1500-2003 time series, except for a loss of power from 1690 to 1790 and since the early 1980s. We hypothesize that these abrupt changes could reflect a physiological response of LBM to past climatic variations. The spatial and temporal variability of LBM outbreaks and the propagation phenomenon in the French Alps highlighted by this study raises questions regarding its future dynamics in response to the expected climate change. Résumé : Dans les écosystèmes forestiers subalpins des Alpes françaises, le mélèze (Larix decidua Mill.) subit périodiquement les épidémies d'un insecte défoliateur, la tordeuse du mélèze (Zeiraphera griseana (Hübner, 1799); LBM). Afin de mieux compren-dre les dynamiques a ` long terme des populations de tordeuse, nous proposons dans cet article une analyse spatio-temporelle d'une très longue reconstruction des épidémies pour la période 1414-2009 sur l'ensemble des Alpes françaises. Cette chronologie a pu être reconstruite a ` partir des cernes de croissance de 44 populations de mélèze. Les résultats ont permis de mettre en évidence le rôle d'un gradient latitudinal que nous avons attribué au phénomène théorique des « épicentres » et « vagues de dissémination ». D'autre part, les analyses temporelles, réalisées a ` l'aide de la méthode des ondelettes, ont révélé l'existence d'un fort signal continu pour des fréquences périodiques de 4, 8 et 16 ans sur l'ensemble de la chronologie a ` l'exception d'une perte d'énergie entre 1690 et 1790 et depuis le début des années 1980. Ces changements pourraient refléter une réponse physiologique de la tordeuse a ` des variations climatiques passées. La variabilité temporelle et spatiale des épidémies de tordeuse ainsi que le mode de propagation a ` travers les Alpes françaises nous ont conduits a ` nous interroger sur les dynamiques futures de l'insecte et de son hôte en réponse au réchauffement climatique rapide dans les écosystèmes de haute élévation. Mots-clés : tordeuse des bourgeons du mélèze, épidémies d'insecte, Alpes françaises, hétérogénéité spatio-temporelle, impact du changement climatique.
Climatic warming disrupts recurrent Alpine insect outbreaks
Proceedings of The National Academy of Sciences, 2010
Climate change has been identified as a causal factor for diverse ecological changes worldwide. Warming trends over the last couple of decades have coincided with the collapse of long-term population cycles in a broad range of taxa, although causal mechanisms are not well-understood. Larch budmoth (LBM) population dynamics across the European Alps, a classic example of regular outbreaks, inexplicably changed sometime during the 1980s after 1,200 y of nearly uninterrupted periodic outbreak cycles. Herein, analysis of perhaps the most extensive spatiotemporal dataset of population dynamics and reconstructed Alpine-wide LBM defoliation records reveals elevational shifts in LBM outbreak epicenters that coincide with temperature fluctuations over two centuries. A population model supports the hypothesis that temperature-mediated shifting of the optimal elevation for LBM population growth is the mechanism for elevational epicenter changes. Increases in the optimal elevation for population growth over the warming period of the last century to near the distributional limit of host larch likely dampened population cycles, thereby causing the collapse of a millennium-long outbreak cycle. The threshold-like change in LBM outbreak pattern highlights how interacting species with differential response rates to climate change can result in dramatic ecological changes.
Trees, 2015
Key message The absence of larch budmoth outbreaks and subsequent consequences on tree rings together with a distinct climate-growth relationship enhance the dendroclimatic potential of larch ring width data from the Tatra Mountains. Abstract Regular population oscillations are generally considered to arise from trophic interactions, though it is unclear how such cycles are affected by biotic and abiotic factors. Cyclic outbreaks of the larch budmoth (LBM; Zeiraphera diniana), perhaps the most prominent example of periodic insect population dynamics, leave distinct ''fingerprints'' in the annual rings of host trees, and have been reconstructed over 1,200 years in the European Alps. Although LBM individuals are known to exist in other regions, it is unclear whether recurrent mass outbreaks historically occurred elsewhere. Here, we present new larch (Larix decidua) host and pine (Pinus cembra) nonhost chronologies from the Slovakian Tatra that comprise 323 ring width samples dating back to 1612 AD. May-June and May-July temperatures control larch and pine growth (r 1951-2011 = 0.63 and 0.57; p \ 0.001), respectively. LBM outbreak-induced defoliation patterns and subsequent ring width reductions were absent over the past three centuries, during which larch (host) and pine (non-host) growth was significantly synchronized (r 1725-2012 = 0.48; p \ 0.001). Spatially limited host forests of overall low stand densities along the northwestern Carpathian arc together with a relatively warm climate envelope are most likely responsible for the absence of cyclic LBM outbreaks. Tree-ring chronologies from these ecotones, free of pulsed disruptions, therefore, represent unique paleoclimatic archives ideal for reconstructing interannual to multi-centennial variations in Eastern European summer temperature.
1200 years of regular outbreaks in alpine insects
Proceedings of the Royal Society B: Biological Sciences, 2007
The long-term history of Zeiraphera diniana Gn. (the larch budmoth, LBM) outbreaks was reconstructed from tree rings of host subalpine larch in the European Alps. This record was derived from 47 513 maximum latewood density measurements, and highlights the impact of contemporary climate change on ecological disturbance regimes. With over 1000 generations represented, this is the longest annually resolved record of herbivore population dynamics, and our analysis demonstrates that remarkably regular LBM fluctuations persisted over the past 1173 years with population peaks averaging every 9.3 years. These regular abundance oscillations recurred until 1981, with the absence of peak events during recent decades. Comparison with an annually resolved, millennium-long temperature reconstruction representative for the European Alps (rZ0.72, correlation with instrumental data) demonstrates that regular insect population cycles continued despite major climatic changes related to warming during medieval times and cooling during the Little Ice Age. The late twentieth century absence of LBM outbreaks, however, corresponds to a period of regional warmth that is exceptional with respect to the last 1000C years, suggesting vulnerability of an otherwise stable ecological system in a warming environment.
2017
Complete List of Authors: Saulnier, Mélanie; Institut Méditerranéen de Biodiversité et d’Ecologie marine et continentale , Aix-Marseille Université, UMR CNRS IRD Avignon Université Roques, Alain; INRA Zoologie Forestiere Guibal, Frédéric; Institut Méditerranéen de Biodiversité, Europôle Méditerranéen de l’Arbois Rozenberg, Philippe; Institut National de la Recherche Agronomique (INRA),, UR0588 Amélioration, Génétique et Physiologie Forestières Saracco, Ginette; Centre de Recherche et d’Enseignement des Géosciences de l’Environnement , CNRS-UMR 7330, AMU Corona, Christophe; GEOLAB CNRS / Université Blaise Pascal / Université de Limoges UMR 6042 , Edouard, Jean-Louis; Aix Marseille Université, CNRS, Ministère de la Culture et de la Communication, CCJ UMR
Frontiers in Forests and Global Change, 2020
Larch budmoth (LBM) periodically defoliates alpine stands of European larch during vast outbreaks occurring generally at 8-10 year intervals. LBM outbreaks recently declined and the ongoing global warming has been pointed out as a possible cause of this decline. In this article, we reconstructed the recent history of LBM outbreaks at different elevations along a larch elevational gradient in the French Alps using direct and indirect observations based on tree-ring width and density analysis, and compared it with local climatic data. We found that LBM outbreaks time-series were better reconstructed with latewood density than with ring width. We also found that there was a recent but limited elevational shift of LBM outbreaks from medium toward higher elevations. We suggest that this elevational shift is a consequence of the variable effect of the global warming at the different elevations. Winter warming is expected to affect differently the timing of LBM egg hatch as well as that of larch bud flush, larvae being at present susceptible to emerge whereas no needles are available as food at the former optimal elevation. A better synchronization between larch and LBM may exist at higher elevations.
Oecologia, 2009
Larch budmoth (LBM, Zeiraphera diniana Gn.) outbreaks cause discernable physical alteration of cell growth in tree rings of host subalpine larch (Larix decidua Mill.) in the European Alps. However, it is not clear if these outbreaks also impact isotopic signatures in tree-ring cellulose, thereby masking climatic signals. We compared LBM outbreak events in stable carbon and oxygen isotope chronologies of larch and their corresponding tree-ring widths from two high-elevation sites (1800-2200 m a.s.l.) in the Swiss Alps for the period AD 1900-2004 against isotope data obtained from non-host spruce (Picea abies). At each site, two age classes of tree individuals (150-250 and 450-550 years old) were sampled. Inclusion of the latter age class enabled one chronology to be extended back to AD 1650, and a comparison with long-term monthly resolved temperature data. Within the constraints of this local study, we found that: (1) isotopic ratios in tree rings of larch provide a strong and consistent climatic signal of temperature; (2) at all sites the isotope signatures were not disturbed by LBM outbreaks, as shown, for example, by exceptionally high significant correlations between non-host spruce and host larch chronologies; below-average July to August temperatures and LBM defoliation events have been coupled for more than three centuries. Dampening of Alps-wide LBM cyclicity since the 1980s and the coincidence of recently absent cool summers in the European Alps reinforce the assumption of a strong coherence between summer temperatures and LBM defoliation events. Our results demonstrate that stable isotopes in tree-ring cellulose of larch are an excellent climate proxy enabling the analysis of climate-driven changes of LBM cycles in the long term.
Impact of climate change on larch budmoth cyclic outbreaks
Scientific Reports, 2016
Periodic outbreaks of the larch budmoth Zeiraphera diniana population (and the massive forest defoliation they engender) have been recorded in the Alps over the centuries and are known for their remarkable regularity. But these have been conspicuously absent since 1981. On the other hand, budmoth outbreaks have been historically unknown in the larches of the Carpathian Tatra mountains. To resolve this puzzle, we propose here a model which includes the influence of climate and explains both the 8-9 year periodicity in the budmoth cycle and the variations from this, as well as the absence of cycles. We successfully capture the observed trend of relative frequencies of outbreaks, reproducing the dominant periodicities seen. We contend that the apparent collapse of the cycle in 1981 is due to changing climatic conditions following a tipping point and propose the recurrence of the cycle with a changed periodicity of 40 years-the next outbreak could occur in 2021. Our model also predicts longer cycles. Model for the Tritrophic System with Climate Parameters Our description of the tritrophic system is represented in the following model (see Methods):
Return of the moth: rethinking the effect of climate on insect outbreaks
Oecologia
The sudden interruption of recurring larch budmoth (LBM; Zeiraphera diniana or griseana Gn.) outbreaks across the European Alps after 1982 was surprising, because populations had regularly oscillated every 8–9 years for the past 1200 years or more. Although ecophysiological evidence was limited and underlying processes remained uncertain, climate change has been indicated as a possible driver of this disruption. An unexpected, recent return of LBM population peaks in 2017 and 2018 provides insight into this insect’s climate sensitivity. Here, we combine meteorological and dendrochronological data to explore the influence of temperature variation and atmospheric circulation on cyclic LBM outbreaks since the early 1950s. Anomalous cold European winters, associated with a persistent negative phase of the North Atlantic Oscillation, coincide with four consecutive epidemics between 1953 and 1982, and any of three warming-induced mechanisms could explain the system’s failure thereafter: (...